As has been shown that, hydrated alumina, for example pseudoboehmites, vary in their suitability for formulating catalysts including a zeolite and a matrix composed of clay and hydrated alumina, and prepared by spray drying the mixture, usually in the forms of microspheres.
As shown in our U.S. Pat. No. 4,086,187, the addition of the ionic polysilicate or a suitable silica sol to such a system employing a pseudoboehmite selected according to the peptizability index results in an improvement in the attrition index, as measured by an abrasion test described in said patent.
A similar observation relating to the utility of various pseudoboehmites is made in the Secor, et al, U.S. Pat. No. 4,010,116.
This patent describes a peptizability index which is somewhat different from the peptizability index of the U.S. Pat. No. 4,086,187. The pseudoboehmite against which the selection is made in both said patents have a relatively high sodium content. U.S. Pat. No. 4,086,187 shows that in a system employing a pseudoboehmite of acceptable peptizability index, the addition of ammonium polysilicate results in an improvement in abrasion resistance.